The present invention relates to an input device for a computer system. More specifically, the present invention relates to an optical coupling assembly for an input device which provides position information to the computer system based on movement of the input device.
A traditional computer input device, such as a mouse, includes a housing with a ball mounted in the housing. The ball is either configured in a traditional manner in which, in the normal work position, the ball engages a work surface and rotates in response to the user""s movement of the mouse across the work surface. The ball may also be provided as a track ball, which is rotated by digital manipulation from the user. In either case, position encoders are used to detect rotation of the ball in the mouse, and to provide position information indicative of that rotation to the computer. In many instances, the position information is used to control movement of a visual image (such as a mouse cursor) on the display screen of the computer.
Also, in one prior device, a computer input device is configured with the track ball arrangement described above. The track ball is preprinted with a uniform predetermined or predefined image. A charge coupled device is used to detect the image on the track ball and detect movement of the image. Movement of the predefined image is used to provide position information to the computer.
However, the prior computer mouse which uses the charge coupled device configuration has a number of significant disadvantages. First, the reaction time of charge coupled devices is quite slow. In addition, processing an image signal from a charge coupled device is computationally intensive and takes a relatively large, and expensive processor. Also, charge coupled devices are highly sensitive to saturation. In other words, if the ambient light conditions are variable, charge coupled devices do not perform well. In addition, if an extraneous light source, such as a relatively bright light, is directed toward the image producing surface, the charge coupled devices can easily become saturated and their performance then quickly degrades.
Further, another prior computer mouse commercially available from Mouse Systems of California included a mouse with an LED which was used in conjunction with a mouse pad having a predetermined, uniform pattern thereon. The pattern was formed by a uniform grid of blue and red lines. The emissions from the LED was reflected off of the: mouse pad to a detector which provided an analog output signal. The signal was in the ,form of a waveshape with peaks corresponding to the different colored grid lines. From this waveform, the lines were counted and interpolated to obtain position information. Such a mouse system requires a mouse pad with a special uniform pattern implemented-thereon.
In the two co-pending patent applications referenced above, an image sensor (such as an imaging array) is used in one illustrative embodiment to detect movement of the computer input device over a work surface. The imaging array can be thought of as taking a picture of the work surface, and analyzing the picture for a pattern or for surface texture or color markings. After waiting an appropriate time, the array takes another picture of the surface and compares it with the previous picture. By finding areas of the two pictures which are the same (or similar), a direction, distance, and/or rotation vector can be determined.
In order for the image sensor to take the picture, a radiation source is used to impinge electromagnetic radiation on the work surface. Radiation reflected from the work surface is reflected back towards the image sensor which captures the image (or takes the picture).
It has been found that many commercially available radiation sources, and in particular light emitting diodes (LEDs), suffer from common problems. The LEDs are typically fabricated with varying degrees of field of view and light uniformity. The field of view is controlled by a primary lens which is typically integrated with the LED housing. The uniformity is -typically dependent on the quality of the silicon die and the placement of the die on -the substrate material. The variation in field of view and uniformity can typically lead to a xe2x80x9cdonutxe2x80x9d shaped image being projected on a surface which resides within a near field.
The present invention provides an optical coupling assembly in a computer input device between a radiation source and an image sensor.
An emitter lens is provided between the radiation source and the work surface to be illuminated. The emitter lens collects radiation and reshapes the illumination pattern to increase intensity and uniformity. The radiation source and emitter lens have associated housings which act to properly orient and align the emitter lens and radiation source. The emitter lens also acts to space the radiation source from an aperture in a housing of the computer input device to provide protection against damage due to electrostatic discharge (ESD).
An imaging lens is provided between the work surface and the image sensor to focus light reflected from the work surface onto the image sensor. An imaging lens housing or holder is provided to properly orient and align the imaging lens with the image sensor. The imaging lens housing provides an apron which increases ESD discharge path length. The imaging lens housing also provides bias members and a lens/sensor interface which act to accurately locate the imaging lens closely proximate the image sensor.